Pressing tool

ABSTRACT

A measurement apparatus is disclosed for a pipe joint assembly (27, 63, 92, 103, 116) to detect the depth of penetration of a pipe end into a press fitting. The measurement apparatus is characterized in that it has an apparatus support (1, 42, 82, 102) that may be set on the outer side of the pipe joint assembly (27, 63, 92, 103, 116), a thickness sensor (23, 24, 74, 75, 90, 113) mounted thereon to detect the thickness of material in the pipe joint assembly (27, 63, 92, 103, 116), and an evaluation device to provide at least a qualitative indication of the detected thickness of material.

The invention relates to a pressing tool for radially compressing a pipeconnection between the pipe end and a press fitting.

Sleeve-shaped press fittings are known to be used for pipe ends whichare plastically deformable and are made of metal, preferably steel. Suchpipe connections and the respective press fittings are described, forexample, in DE-C-11 87 870 and DE-C-40 12 504. For the manufacture ofthe connection, the pipe end and the press fitting are pushed into eachother axially and, thereafter, they are force- and form-tightlyconnected via a pressing tool which is mounted on the press fitting bypressing jaws which are movable toward each other.

The reliability of the connection between the pipe end and the pressfitting depends, among other things, on the fact that the pipe end ispushed into the press fitting at a determined minimum insertion depth.The insertion depth is delimited by a constriction in the press fitting.Thereby, the axial distance from the constriction to the end into whichthe pipe end is to be pushed is greater, the greater the circumferenceof the pipe end or the press fitting is. The constriction forms, at thesame time, a stop to prevent the further insertion of the pipe end.

The arrival at the minimum insertion depth depends of the reliabilityand the feeling of the mounter. Especially under limited spaceconditions, the insertion of the pipe end into the press fitting can beimpaired and, therefore, it can come to jamming before the constrictionis reached, which has the consequence that the minimum depth is notreached and the mounter erroneously does not notice it. As an additionalcontrol, it has been suggested to provide markings for the minimuminsertion depth on the outside of the pipe. Special measuring apparatushave been developed for this purpose (DE-GM 92 16 760.8). Even the useof marking apparatus does not provide an absolute security againstincorrect manipulation. Furthermore, the markings can be inadvertentlywiped off.

In DE-C-40 12 504, a process is proposed, which allows a compressiononly then, when an axial force is applied with the help of a devicearranged on a pressing tool, whereby the compression is only thendecoupled, when the axial force exceeds a determined threshold value. Inthis process, it is assumed that the threshold value is only exceededwhen the pipe end collides with the constriction. Besides the fact thata correspondingly built arrangement for seizing the axial forces must beprovided for this process, the process also does not sufficiently ensurethat the threshold value for the axial force is only reached when thepipe end actually collides against the constriction.

A process is known from JP-A-57-142507, wherein the position of a rubberring, which is arranged on the inside of a pipeline faucet and invertedover a pipe end, can be determined. For this purpose, an oscillationsource is moved along a pipe axis inside the pipe. An oscillation sensoris placed in the front area of the pipe and measures the change in theoscillation behavior in dependence upon the movement of the oscillationsource. The position of the rubber ring between pipeline faucet and pipeend can be determined based on these changes.

This process is not for determining the insertion depth of the pipe endand, additionally, presupposes that the measuring apparatus with theoscillation source and the oscillation sensor can be guided in from theinside. The process, therefore, is not useful for the measurement of theinsertion depth in a pipe connection of the present art.

Therefore, the invention has as its object to provide a means for asecure control of the insertion depth between a pipe end and a pressfitting in a pipe connection.

The object of the invention is solved in that the measuring apparatusfor measuring the insertion depth of the pipe end is provided in thepress fitting, which has a thickness sensor for the measurement of thematerial strength of the pipe connection as well as an interpretationdevice for the at least qualitative display of the measured materialstrength on the pressing tool. For this purpose, ultrasound sensors,magnetic field sensors and/or eddy current sensors can be especiallytaken into consideration for the thickness sensor. Also, thicknesssensors based on other physical effects can be considered, which areable to measure the material thickness of the pipe connection.

The basic idea of the invention relies also on the further measurementof the insertion depth with the help of a measuring apparatus which iscapable of measuring the material thickness of the pipe connection. Forthis purpose, it is enough that this measuring apparatus can provide thequalitative difference between the material thickness of the pressfittings alone and the material thickness which is formed by thecombination of the material thickness of the press fittings and of thepipe end. The difference is prepared by an interpretation device in sucha manner that the person performing the work receives the correspondingoptical or acoustic information. It can be created as a warninginformation in the case when the measuring apparatus measures only thematerial thickness of the press fittings. However, a quantitativeindication for the corresponding measured material thickness is alsopertinent.

As a rule, a pressing tool equipped in this manner is useful only forthe compression of pipe connections of a very determined diameter sothat an arrangement of the thickness sensor is then sufficient whichcomes to lie over the insertion depth provided. Since the pressing tool,or parts thereof, is to be used for the compression of pipe connectionsof different diameters, it is recommended to provide at least one radialdisplacement device--preferably in combination with an axialdisplacement device--to adapt the thickness sensor with respect to itsaxial and radial position on the respective diameter of the pipeconnection in such a manner that the control of the pipe end is possibleafter reaching the respective preset insertion depth.

The invention is further explained in the drawings with the help ofembodiments.

FIG. (1) shows a pressing tool with thickness sensor in frontal view;

FIG. (2) shows an axial section through a pipe connection with thepressing tool according to FIG. 1 in the plane B-C;

FIG. (3) shows the axial section according to FIG. 2 with the pipe endinserted;

FIG. (4) shows a front view of a pressing tool with thickness sensor.

The pressing tool (1) of FIG. 1 shows a ground plate (2), which iscomprised by an approximately heart-shaped end piece (3) and a holdingplate (4) continued downwardly. Pressing levers (5, 6) are pivotallyconnected to the end piece (3) over joint bolts (7, 8).

The corresponding upper lever arms (9, 10) of the pressing lever (5, 6)have opposite lying grooves (11, 12). As can be seen in FIGS. 2 and 3especially, the grooves (11, 12) are delimited by the pressing jaws (13,14), which are located in the lever arms (9, 10) and held thereon.

The pressing levers (5, 6) have lower lever arms (15, 16), which haveforking surfaces (17, 18) on their mutually opposite sides and whichhave a distance which diminishes conically in the direction of the jointbolts (7, 8). On the holding plate (4), two forking surfaces (19, 20)are positioned one beside the other on a slide (not shown here). Theslide can be moved in the direction of the arrow (A) by means of amountable drive device. In this way, the forking rolls (19, 20) runagainst the forking surfaces (17, 18) and push the lower lever arms (15,16) apart. This, further, has the result that the upper lever arms (9,10) are moved toward each other.

On the end piece (3), and particularly on the right joint bolt (8),holders (21, 22) are provided on each side, which hold on each free enda respective horizontally extending ultrasound sensor (23, 24) of aknown construction. Electrocables (25, 26) protrude out of the rear endof the ultrasound sensors (23, 24) and lead to a measuring apparatus(not shown here). Here also, the measuring apparatus is of a known typewhich is commonly available in the marketplace.

As can be seen especially in FIGS. 2 and 3, the pressing jaws (13, 14)encompass a pipe connection (27). The pipe connection consists of a pipeend (28) and a press fitting (29) known from the art. The press fitting(29) is only represented partially and has, on the end facing the pipeend, a ring-shaped bulge (30) on the inner side of which a sealing ring(31) is placed which is made of elastomeric material. At a distance fromthe ring-shaped bulge (30), the press fitting (29) has a constriction(32) which forms a stop for the pipe end (28).

In FIG. 2, the pipe end (28) is not inserted up to the constriction(32), but stops before the ultrasound sensor (23). The same measuresthereby only the material thickness, that is, the wall thickness of thepress fittings (29). This is shown correspondingly on the interpretationdevice, for example, by a digital display or through a warningindication of an acoustic or optic kind. Thereby, the interpretationdevice with the drive device for the pressing tool (1) can be coupled insuch a manner that the drive device cannot be operated as long as theultrasound sensor only measures the wall thickness of the press fittings(29). In this way, a faulty manipulation of the pressing tool (1) isautomatically avoided.

In FIG. 3, the pipe end (28) is inserted into the insertion depthprovided up to the constriction (32). The ultrasound sensor (23)measures now not only the wall thicknesses of both the press fittings(29) and the pipe end (28) but also the double material thickness. Theinterpretation device shows this correspondingly and sets the drivedevice for the pressing tool free, insofar a direct connection existsbetween both.

The pressing effect per se can only begin by operation of the drivedevice. As described above, the forking rolls (19, 20) run between thelower lever arms (15, 16) and so pivot the upper lever arms (9, 10)against each other, whereby the press fitting (29) and the pipe end (28)are radially compressed. In this way, the ring-shaped bulge (30) ispushed against the pipe end (28) so that the sealing ring (31) ispressed on the pipe end (28) with the radial strength needed for a goodseal.

As can be seen in FIGS. 2 and 3, the pressing jaws (13, 14) are shapedsymmetrical. This means that the pressing tool (1) can be placed andoperated on opposite sides. So as to be able to exert a control of theinsertion depth of the pipe end (28) in this case also, the secondultrasound sensor (24) is attached on the other side of the pressingtool (28). The ultrasound sensor (24) is not necessary when the pressingjaws (13, 14) have an asymmetric shape, which allows a positioning ofthe pressing tool only in one position, or when other arrangementsprevent the positioning in an erroneous position as described in DE-GM92 16 369.6.

In FIG. 4, a pressing tool (41) is provided, as seen in individualexamples in DE-GM 92 16 369.6. The pressing tool (41) has a pressingring (42) with five practically identically shaped pressing jaw elements(43, 44, 45, 46, 47). Therefore, each pressing jaw element is comprisedof outer pressing jaw carriers (48, 49, 50, 51, 52) and an innerarc-shaped pressing jaw. All except of the pressing jaw carriers (48,49, 50, 51, 52) are joint-connected over the intermediate pieces (53,54, 55, 56).

The lower pressing jaw elements (43, 47) in this view have a closingslit (57) between them. The free ends of these pressing jaw elements(43, 47) carry joint bolts (58, 59) on each of which a coupling latch(60, 61) is hung. When the coupling latches (60, 61) are placed in theposition indicated by a line-and-dot line, so that they are not coupledtogether, the pressing ring (42) can by positioned over a pipeconnection (63) which consists of a press fitting and a pipe end. Thisis shown in the drawing. Then, both lower pressing jaw elements (43, 47)are pivoted toward each other until the coupling holes (64, 65) providedon their free ends are aligned with each other. The coupling bolt (66),which is connected to an operating lever (67), is pushed through thesecoupling holes (64, 65). By moving the operating lever (67) by 180°, theconnection between the two coupling latches (60, 61) can be shortenedsomewhat and the pressing ring (42) is thereby tightened in such amanner that it sits firmly on the pipe connection (63). For thispurpose, the coupling bolt (66) is shaped as an eccentric bolt as can beseen from DE-GM 92 16 369.6. Reference is made to this because it is notnecessary for the function of the present invention.

A U-latch is fastened to the joint bolts (68, 69) of the upper pressingjaw elements (45). A U-handle is attached to the left end in the axialmiddle plane of the pressing tool (41). The U-handle (71) is pivotedfrom the position represented as a line-and-dot line to the positionrepresented as a solid line and is connected over the coupling elements(72, 73) to the U-latch (70). The inner edge of the U-latch (70) and theU-handle (71) forms a closed circle concentric with the pipe connection(63).

Semicircular induction spools (74, 75) are placed in the U-latch (70),on the one hand, and on the U-handle (71), on the other hand, and form aclosed cylinder-shaped induction spool in the closed position shown. Theinduction spools (74, 75) can be provided with alternate current via acable (76) and an entrance position (77). This has the consequence thatan eddy current is originated, with an inductivity which depends on thematerial thickness of the pipe connection (63) in the region of theinduction spools (74, 75).

The induction spools (74, 75) have an axial distance to the pressingring (42) such that the pressing ring (42) is correctly set in placearound the ring-shaped bulge (not shown here) or the press fittings areplaced in a certain position which is comparable with the position ofthe ultrasound sensor (23) in the exemplary embodiment according toFIGS. 1 to 3, that is, in the immediate vicinity of the constriction ofthe press fitting. In this way, the inductivity, when only a pressfitting is present in this region because the corresponding pipe end isnot inserted sufficiently deep into the press fitting, is different fromthe inductivity which is present when the pipe end is completelyinserted. This can be measured with methods not represented herein andcan be transmitted to the interpretation device (also not shown) fordisplaying the two situations.

I claim:
 1. Pressing tool (1, 41) for radially compressing a pipeconnection (27, 63) between a pipe end (28) and a press fitting (29),characterized in that an apparatus is provided for attachment to thepressing tool, said apparatus for ascertaining the insertion depth ofthe pipe end (28) into the press fitting (29), said apparatus includes athickness sensor (23, 24, 74, 75) for measuring the material thicknessof the pipe connection (27, 63) and an interpretation device for atleast the qualitative display of the measured material thickness. 2.Pressing tool according to claim 1, characterized in that the thicknesssensor (23, 24) is an ultrasound sensor.
 3. Pressing tool for formingthrough radial compression a pipe connection between a pipe end and apress fitting, comprising:a) a tool for radially compressing a pressfitting about a pipe end after the pipe end has been positioned apredetermined distance within the pipe fitting; and b) an apparatusattachable to the tool for determining whether the pipe end has beeninserted the predetermined distance within the pipe fitting, saidapparatus comprising a thickness sensor for measuring the thickness ofthe pipe end and pipe fitting material at a predetermined location alongthe pipe fitting and an interpretation device for displaying themeasured material thickness.
 4. The tool of claim 3, wherein:a) saidthickness sensor is an ultrasound sensor.
 5. The tool of claim 4,wherein:a) said interpretation device is chosen from the groupconsisting of digital displays, acoustic indicators, and opticalindicators.
 6. The tool of claim 3, wherein:a) said interpretationdevice is chosen from the group consisting of digital displays, acousticindicators, and optical indicators.
 7. The tool of claim 3, wherein:a)there are at least two thickness sensors, and said tool is disposedbetween said sensors.